semi-noobie question about steel...

BryFry

BryFry

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Hey, I read a few years ago about cryo-treating steel where they take blades and subject them to super sub-zero temps, and this is supposed to greatly increase their edge holding ability. I haven't heared anything more about it recently, and was wondering if this was just a "gimmic" or does it realy have an effect? -and if so, which makers/manufacturers use this technique?

Also we all know that titanium is strong and "rust-proof", and I know there are blades made from the stuff, but I haven't heared much about it. I'm assuming there are downsides to it, but I'm currious how well it holds an edge.

And, I was wondering if there are any knives made from Tungston carbide steel, and what its properties are like?
 
Hello there,

I know for certain that SOG knives use the cryo treatment on several of their AUS 8 blades such as the SOG Trident and Flash series. I have to admit that they really do seem to hold an edge longer than AUS 8 from other reputable companies.

As for Titanium, it is rustproof and there are some knives made completely of it, pins, screws, and all. The edge doesn't stay/get razor sharp like normal blade steels, but if you plan on doing a lot of offshore/salt-water fishing, or you don't like doing routine maintenance, an all titanium knife would work, but would be pricey. H-1 steel from Spyderco knives would be better as a rust proof steel as it uses nitrogen instead of carbon and therefore can't rust. It also holds an edge comparable with AUS 8.

Last but not least, I have no idea about tungsten carbide blades :D

I hope this helps, J.
 
Cryo reduces retained austenite after primary quenching and converts it to the hard martensite. It works best on complex alloys. The trade offs seem to be cost and a possible decrease in toughness.

A tungsten carbide blade would be brittle as hell. Special attention must be paid to tools made from tungsten carbide. They're expensive and have a tendency to break. A solid-carbide blade would have to be ground with diamonds, too, adding to cost.
 
Phillip Dobson said:
A tungsten carbide blade would be brittle as hell. Special attention must be paid to tools made from tungsten carbide. They're expensive and have a tendency to break. A solid-carbide blade would have to be ground with diamonds, too, adding to cost.
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Sweet, I became currious about Tungsten after purchasing a Tungsten carbide wedding band for myself, and being told that if I ever had a misshap involving that ring and finger, that they would have to remove my finger since they don't have tools that will cut through the ring.

Scary thought, since I did just smash off the end of my middle finger a month ago. Must say tungsten is pretty cool though, been wearing it every day for two years and it still has a perfect mirror pollish, no scratches at all!

Too bad it's brittle for blades... maybe some kind of laminated steel mix would work? :D
 
Pretty much all the better knives you can buy today have been cryo treated. Now don't get me wrong, I have fewer than 150 knives so I am by no means a knife collector, but the only knives I own that have not been cryo treated are antiques made from low-alloy carbon steels. Over time the retained austenite transforms into untempered martensite anyway, basically the same as cryo treating, so the knives are kind of brittle now.
 
BryFry said:
Sweet, I became currious about Tungsten after purchasing a Tungsten carbide wedding band for myself, and being told that if I ever had a misshap involving that ring and finger, that they would have to remove my finger since they don't have tools that will cut through the ring.

Scary thought, since I did just smash off the end of my middle finger a month ago. Must say tungsten is pretty cool though, been wearing it every day for two years and it still has a perfect mirror pollish, no scratches at all!

Too bad it's brittle for blades... maybe some kind of laminated steel mix would work? :D
Click to expand...

What experience I've had with SOG's AUS8 was pretty good. Got sharp, stayed that way long enough for my needs, didn't develop any rust and seemed tough enough for most tasks. Not amazing but very usable.

I went with a titanium wedding band because I was told the tungsten band would shatter if hit hard enough. Mine shows scratches, though.

Oh, and welcome

Frank
 
BryFry said:
Sweet, I became currious about Tungsten after purchasing a Tungsten carbide wedding band for myself, and being told that if I ever had a misshap involving that ring and finger, that they would have to remove my finger since they don't have tools that will cut through the ring.

Scary thought, since I did just smash off the end of my middle finger a month ago. Must say tungsten is pretty cool though, been wearing it every day for two years and it still has a perfect mirror pollish, no scratches at all!

Too bad it's brittle for blades... maybe some kind of laminated steel mix would work? :D
Click to expand...

I wear a tungsten carbide wedding band. You can get a tungsten carbide ring off with a pair of vise grips if you know what you're doing. Close the vise, then adjust it so it's tight on the ring and open it again. Then tighten it just a little, and close it again on the ring. You'll start the ring cracking. Open the vise, move it over to an adjacent part of the ring and close it again- you'll get some more cracking. Keep opening and closing the vise all around the ring. Tighten the vise again a small amount if you need to. Eventually the ring will break apart.

That silliness about removing the finger is just people who don't know what they're talking about so they say something dramatic.

BTW, there are already steels that include enough tungsten to form carbides- so you have steel that includes tungsten carbide. Very wear resistent.
 
Ha, yes, I was in your same position not long ago (though not quite to the same extent):D
Tungsten is indeed a very need element, it is super hard, and has the highest melting pt of all metals. What you want is a High speed steel . High speed steels are steels used for cutting (usually metal) so rapidly that the cutting blade may become visibly hot. these steels sometimes have as much as 10%-15% W, and 5%-10% vanadium another very cool alloying element. The W and Molybdenum allow it to retain its hardness (which is often very high 60-73 HRC) at very high temperatures. in fact HSS are used to bridg the gap betwixt normal steel and Carbide. May I suggest CPM M4 it is hard 60-63 and tough. if ever there was a perfect steel CPM M4 is it.

M4 http://www.crucibleservice.com/datash/dsM4v8.pdf?CFID=367031&CFTOKEN=76584832

http://www.crucibleservice.com/eselector/prodbyapp/highspeed/highspeedapptitle.html
 
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Oh by the way about cryo treatment it is really just another way of tempering the steel.
what happens after hardening is that you get some martensite (good), and some Austenite (not so good). In traditional tempering raising the temperature increasing the temp make the steel more ductile so that the remaining Austenite can be transformed into Martensite, while at the same time relieving internal stress.

Cryo treatment lowers the temp such that this transformation can take place even in the no ductile cod steel
 
Nebulae said:
Ha, yes, I was in your same position not long ago (though not quite to the same extent):D
Tungsten is indeed a very need element, it is super hard, and has the highest melting pt of all metals. What you want is a High speed steel . High speed steels are steels used for cutting (usually metal) so rapidly that the cutting blade may become visibly hot. these steels sometimes have as much as 10%-15% W, and 5%-10% vanadium another very cool alloying element. The W and Molybdenum allow it to retain its hardness (which is often very high 60-75 HRC) at very high temperatures. in fact HSS are used to bridg the gap betwixt normal steel and Carbide. May I suggest CPM M4 it is hard 60-63 and tough. if ever there was a perfect steel CPM M4 is it.

M4 http://www.crucibleservice.com/datash/dsM4v8.pdf?CFID=367031&CFTOKEN=76584832

http://www.crucibleservice.com/eselector/prodbyapp/highspeed/highspeedapptitle.html
Click to expand...

They now have CPM M4 + Cobalt modification called CPM REX 54, check it out:

http://www.crucibleservice.com/eselector/prodbyapp/highspeed/cpm54.html

Highest attainable hardness is 66.5 rc compared to M4's 65.5.
 
Titanium is strong and also very light, but has severe trade-offs which combined with the expense (it's scarcer and harder to work) make it rarely used for knives. It's extremely difficult to get a sharp edge, and it holds an edge very poorly. In addition to corrosion resistance (and there are other far cheaper metals with fewer trade offs that don't corrode) it's non magnetic. This isn't likely to matter much to Joe average people like me, but for specialized applications it's a must--note that Mission Knives' (well respected)
Ti blades are geared towards mine or bomb disposal. If you want a Ti knife that's beyond a novelty item, Mission would be the way to go.

Never heard of tungsten carbide wedding bands, interesting. All I remember about tungsten is that Edison tried many MANY things for light bulb filaments but they invariably melted/shorted out in short order. Tungsten was the solution, though given the fragility of light bulb filaments you can see the problem with brittleness. Good for filaments, not good for knives.
 
Wow! Thanks for the all the info, very indepth, love to learn all I can about knives and steel.

Question; Does anyone know when SOG started useing cryo treatment? I have a Seal 2000, sogwinder, and Pentagon, all perchased around 1995, I'm wondering what steel and treatment they used back then? I know my sogwinder folder doesn't hold an edge as well as I'd like.... still like the knife though.
 
CPM 121 is very similar HRC 70.5 after ht and temper.

I saw the M 54, it looks good harder, but the crucible pdf didnt really list comparable toughness gauge (no charpy, or bend fracture)

darn I was just talking to the people at crucible (Scott), they were really nice shoulda asked. woulda if id known
 
what Heat Treating companies would you guys suggest.

I need to get some CPM M4 HT, and obviously I want them to do a fantastic job.
Oh, and if they have a branch, or something in Texas That would be great.
 
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